Assessment of HVDC technologies for an offshore MTDC grid
File(s)
Author(s)
Sheridan, Caitríona Evelyn
Type
Thesis
Abstract
This thesis examines various HVDC converter technologies that could be used in offshore Multi-Terminal DC (MTDC) grids. MTDC grids rely on AC/DC converters to interface with AC systems and also for control services. Two AC/DC topologies were compared, the half-bridge Modular Multi-level Converter (MMC) and the Alternate Arm Converter (AAC). As new DC system voltages emerge the DC/DC converter could be an enabling technology for interconnection and future MTDC networks. As yet there is no consensus on DC/DC converter topology and a critical comparison of several potential designs was conducted. An MMC based DC/DC converter had distinct advantages compared with other designs. Several average value converter models of the converters were developed to allow efficient simulation of MTDC networks, while maintaining a high level of accuracy of the converter characteristics. These models were verified with full switching models for steady state and fault conditions. Two o shore MTDC networks were studied; a four-terminal network, and a MTDC network. The four-terminal network used a normally open point to connect two existing point-to-point links, allowing reconfiguration in the event of a DC fault. The MTDC network uses a DC/DC converter to interconnect a bipole
HVDC link with the previously studied four-terminal network. Several simulation studies show how new converters can improve the operation of a MTDC and provide additional capabilities such as DC fault blocking.
HVDC link with the previously studied four-terminal network. Several simulation studies show how new converters can improve the operation of a MTDC and provide additional capabilities such as DC fault blocking.
Version
Open Access
Date Issued
2015-10
Date Awarded
2016-02
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Green, Timothy
Sponsor
Arup
National Grid plc
Publisher Department
Electrical and Electronic Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)